The present invention relates to a container which can be closed in a gastight manner for the storage, transport and, optionally, the sedimentation of substances which are solid at room temperature and can be introduced in or taken out in a molten state under a vacuum or, preferably, under protective gas. In particular, the container is for handling lithium metal which optionally contains solid impurities in the melt. The container of the invention is provided with a cylindrical middle section and a lower and an upper dished container end which has a manhole. The present invention also relates to the process of using the described apparatus.
The purpose of the invention is to be able to maintain such a container sufficiently warm in a broad temperature range between room temperature and 600.degree. C. under the condition of a minimum temperature difference between the location of the associated heat source for the container and the most distantly removed container surfaces.
Up to the present, molten alkali metals, for example, such as sodium or lithium were produced according to the fusion electrolysis process and maintained in liquid condition in containers until they were subsequently formed into solid blocks. The necessary heating energy was supplied to these containers either by heat exchange oil or by heating elements attached to the outside of the container wall.
This type of energy supply has several disadvantages. When oil is used as heat exchange medium, the engineering expense for operating the oil circulation system is very high. When the oil temperature is changed, especially when the heating and cooling device is turned on and off, expansions on the flanges of cooling jackets and lines cause leaks from which oil drips. The problems which occur, especially in the area of operational safety, are so significant that industrial standard regulations such as the VDI and DIN had to be issued. Moreover, tempering operations are possible only up to a certain limiting temperature. The highest temperature at which a container can be heated in a practical manner with heating oil is approximately 350.degree. C. A constant purification of the heating circuits is necessary on account of the cracking of the heat exchange oil.
The use of associated electrical heating apparatus, e.g. by means of heating elements, heating mats or heating muffs attached to the outside of the container is expensive in respect of installation and maintenance. When such a container is cleaned on the inside and the outside with water or solvents, the associated heating apparatus must be dismantled and then reassembled.